diff --git a/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/functions/scalar/DateDiff.java b/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/functions/scalar/DateDiff.java
index 0595f70ea0370a..e581b7c3598f66 100644
--- a/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/functions/scalar/DateDiff.java
+++ b/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/functions/scalar/DateDiff.java
@@ -40,11 +40,11 @@ public class DateDiff extends ScalarFunction
         implements BinaryExpression, ExplicitlyCastableSignature, PropagateNullableOnDateLikeV2Args {
 
     public static final List<FunctionSignature> SIGNATURES = ImmutableList.of(
+            FunctionSignature.ret(IntegerType.INSTANCE)
+                    .args(DateTimeV2Type.SYSTEM_DEFAULT, DateTimeV2Type.SYSTEM_DEFAULT),
             FunctionSignature.ret(IntegerType.INSTANCE).args(DateV2Type.INSTANCE, DateV2Type.INSTANCE),
             FunctionSignature.ret(IntegerType.INSTANCE).args(DateV2Type.INSTANCE, DateTimeV2Type.SYSTEM_DEFAULT),
             FunctionSignature.ret(IntegerType.INSTANCE).args(DateTimeV2Type.SYSTEM_DEFAULT, DateV2Type.INSTANCE),
-            FunctionSignature.ret(IntegerType.INSTANCE)
-                    .args(DateTimeV2Type.SYSTEM_DEFAULT, DateTimeV2Type.SYSTEM_DEFAULT),
             FunctionSignature.ret(IntegerType.INSTANCE).args(DateTimeType.INSTANCE, DateTimeType.INSTANCE)
     );
 
diff --git a/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/functions/scalar/DaysDiff.java b/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/functions/scalar/DaysDiff.java
index 3f12ba2d74f147..e0343f1148f162 100644
--- a/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/functions/scalar/DaysDiff.java
+++ b/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/functions/scalar/DaysDiff.java
@@ -40,11 +40,11 @@ public class DaysDiff extends ScalarFunction
         implements BinaryExpression, ExplicitlyCastableSignature, PropagateNullableOnDateLikeV2Args {
 
     private static final List<FunctionSignature> SIGNATURES = ImmutableList.of(
+            FunctionSignature.ret(BigIntType.INSTANCE)
+                    .args(DateTimeV2Type.SYSTEM_DEFAULT, DateTimeV2Type.SYSTEM_DEFAULT),
             FunctionSignature.ret(BigIntType.INSTANCE).args(DateV2Type.INSTANCE, DateV2Type.INSTANCE),
             FunctionSignature.ret(BigIntType.INSTANCE).args(DateV2Type.INSTANCE, DateTimeV2Type.SYSTEM_DEFAULT),
             FunctionSignature.ret(BigIntType.INSTANCE).args(DateTimeV2Type.SYSTEM_DEFAULT, DateV2Type.INSTANCE),
-            FunctionSignature.ret(BigIntType.INSTANCE)
-                    .args(DateTimeV2Type.SYSTEM_DEFAULT, DateTimeV2Type.SYSTEM_DEFAULT),
             FunctionSignature.ret(BigIntType.INSTANCE).args(DateTimeType.INSTANCE, DateTimeType.INSTANCE)
     );